Ethanol Concentration Management in Syngas Fermentation
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Solution Overview
Problem
Ethanol concentration during syngas fermentation increases to inhibitory levels, leading to reactor failure and decreased productivity, necessitating a process to balance ethanol removal with maintaining desired cell density and productivity.
Innovation Solution
A process involving inoculating a medium to achieve a cell density of at least 0.1 grams per liter, separating cells and medium to provide concentrated cells and permeate, separating ethanol from the permeate to create a reduced ethanol aqueous stream, and returning it to the fermentation, with a ratio of return stream to removal rate ranging from 0.5 to 25, effectively managing ethanol concentration and maintaining high productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ethanol concentration increases during fermentation, then productivity improves, but reactor failure occurs due to inhibitory levels
Solution Approach 1:
The patent implements a feedback control system where ethanol concentration is continuously monitored and the fermentation process is adjusted accordingly. When ethanol reaches inhibitory levels, the system automatically reduces feeding rate or increases dilution to maintain productivity while preventing reactor failure.
Solution Approach 2:
The patent dynamically changes process parameters including feeding rate, dilution rate, and aeration based on real-time ethanol concentration measurements. By adjusting these parameters, the system maintains ethanol production at high levels without allowing inhibitory concentrations to develop, thus resolving the contradiction between productivity and reliability.
2Quantity of substance
If cells and medium are removed to maintain cell density, then cell density is maintained, but ethanol concentration increases to inhibitory levels
Solution Approach 1:
The patent selectively removes cells from the fermentation medium through continuous filtration or centrifugation systems. By extracting only the cellular biomass and returning the cell-free medium to the fermenter, the system maintains cell density at optimal levels while preventing ethanol accumulation to inhibitory levels, thus resolving the contradiction between cell density maintenance and ethanol concentration control.
Solution Approach 2:
The patent segments the fermentation process into separate functions: cell growth occurs in the fermenter while ethanol removal and medium recycling occur in separate units. This segmentation allows independent optimization of cell density maintenance and ethanol concentration control without compromising overall productivity.
3Reliability
If ethanol removal rate increases to prevent inhibitory levels, then reactor stability is maintained, but productivity decreases
Solution Approach 1:
The patent implements a system where ethanol-containing medium is continuously removed, ethanol is recovered through distillation or extraction, and the depleted medium is returned to the fermenter. This approach maintains reactor stability by preventing inhibitory ethanol levels while recovering and accounting for the removed ethanol in productivity calculations, thus resolving the contradiction between stability and productivity.
Solution Approach 2:
The patent maintains continuous operation by continuously removing and recovering ethanol rather than batch removal. This continuous process ensures reactor stability is maintained at all times while maximizing overall ethanol production throughput, resolving the contradiction between stability and productivity through uninterrupted operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process stabilizes fermentation, achieving space time yields (STY) of at least 10 g/(L·day) to 200 g/(L·day) by balancing cell and medium removal with ethanol recycling, preventing reactor failure and maintaining high ethanol production.
Implementation Method 1
A distillation column receives permeate from the permeate holding tank. The distillation column is effective for separating ethanol from the permeate to provide ethanol and a reduced ethanol aqueous stream.
Data Source
AI summary
A process is provided for management of ethanol concentration during syngas fermentation. A process for fermentation of syngas includes inoculating a medium to provide an inoculated medium. Inoculated medium is contacted with syngas and cells and medium are removed and separated to provide concentrated cells and permeate. Ethanol is separated from the permeate to provide ethanol and a reduced ethanol aqueous stream. The reduced ethanol aqueous stream is returned to the fermentation.